The present invention relates to a piston engine having at least one first piston and at least one first housing.
Heat engines are used for conversion of chemical energy into mechanical energy, from thermal energy into mechanical energy and from mechanical energy into thermal energy. Internal combustion engines as a heat engine convert chemical energy into mechanical energy, Stirling engines as a heat engine convert thermal energy into mechanical energy and heat pumps as a heat engine convert mechanical energy into thermal energy. One of the most frequently used heat engines is the piston engine, in which mechanical energy is transmitted from a piston to a shaft by a connecting rod.
An alternative construction is provided by the free-piston engine. A free-piston engine is a piston engine without a connecting rod. Free-piston engines are used for example as a pump for a hydraulic system or in conjunction with a linear generator for the direct generation of electrical energy.
Regardless of whether a heat engine is designed as a conventional piston engine or as a free-piston engine, during operation friction usually occurs between the piston and the cylinder, which leads to wear. In time, the wear results in a limited function or leads to destruction of the heat engine. A conventional solution of the problem of friction or wear is effected by lubrication of the engine. Lubrication reduces the mechanical friction between the piston and the cylinder, but does not completely remedy the problem of wear. Particularly transverse forces which can act upon the piston, for example depending upon the position of a connecting rod, represent a possible cause for the wear of the piston-cylinder system, which is not remedied by lubrication. Lubrication via an oil pump furthermore involves problems when the engine is being started if the oil pump is operated via the crankshaft, and at low rotational speeds of the heat engine, during which only a low oil pressure is created.
Wear leads to a significant reduction of the service life of engines. In motor vehicles, for example, wear can lead to a reduction of the service life by 10,000 operating hours and in diesel engines of construction machines wear can lead to a reduction of the service life by up to 15,000 operating hours.
The use of lubrication also leads to problems. In internal combustion engines, some of the lubricating oil is always burnt in addition and so leads inter alia to an increased loading of the environment. Lubricating oils are destroyed as a result of contaminants and as a result of the forces exerted upon them, which is why in the case of lubricated engines high maintenance cost is incurred as a result of the regularly necessary exchange of the lubricant.